8. No growing crop certificate may be issued containing a statement that seed potatoes are capable of being marketed as basic seed potatoes of any grade unless the authorised officer is satisfied that the immediately succeeding crop produced from the seed potatoes is not likely to contain—U.K.
(a)more than 0.25% by number of growing plants which do not breed true to variety or are a different variety; and
(b)in the case of—
(i)Union grade S, not more than 1%,
(ii)Union grade SE, not more than 2%, and
(iii)Union grade E, not more than 4%,
by number of growing plants which show symptoms of virus diseases prevalent in Europe where those symptoms are attributable to infection in the mother crop.